Reenforcing thread applying means for sewing machines



y 1937- L. A. CUNDALL ET AL REENFORCING THREAD APPLYING MEANS FOR SEWING MACHINES Fil'ed Aug. 6, 1935 2 Sheets-Sheet l 4 /AIVAIIIVA ATTORNEY.

y 1937- A. CUNDALL ET AL 2,081,793

REENFORCING THREAD APPLYING MEANS FOR SEWING- MACHINES Filed Aug. 6, 1955 2 Sheets-Sheet 2 mummy;

4 ATTORNEY.

' INVENTORS Patented May 25, 1937 UNITED STATES PATENT OFFICE REENFORCIN'G THREAD APPLYING MEANS FOR SEWING MACHINES ApplicationAugust 6, 1935, Serial No. 34,870

2 Claims.

Our present invention relates to an improvement in sewing machines by means of which articles and materials may be stitched in such fashion that the seam is reenforced by reenforcing threads which prevent the sewing thread from tearing through the materials. In particular, the invention is designed to be applied to a sewing machine adapted to stitch multi-ply paper bags of the types in use for packaging granular or pulverulent materials, such as soda ash, flour or the like, in packages of from 50 to lbs., more or less. The object of such stitching is to provide a neat, effective seam which will be as strong as the paper or fabric from which the bags are made and over which may be placed a tape made, for example, of craped kraft paper, designed to block the needle holes and to cover the ends of the plies of the bag whereby to prevent egress of material and ingress of moisture or foreign matter.

The present invention is an improvement upon the invention of Robert N. Cundall disclosed and claimed in United States Letters Patent No. 1,963,652, dated June 19, 1934. The object of the present invention is to create a seam constituting an improvement upon the seam disclosed and claimed in United States Letters Patent No. 1,913,825, issued to Webster Noyes Baker, dated June 13, 1933. Specifically, the present seam comprises two small reenforcing threads taking the place of the one large reenforcing cord be neath the needle thread disclosed in the aforementioned patents.

The advantages of the present invention over the prior inventions are, first, that the needle thread is maintained in a straight line instead of being alternately twisted to opposite angular relationship with the line of the seam, thereby forming a better seam. A second advantage of the present invention is that the resulting reenforced seam is not as thick as the prior seam, whereby the sealing tape may be better bonded to the plies of the bag and whereby a more uniform spacing of thestitches is accomplished because of lesser interference with the action of the sewing machine.

Another object of the present invention is to devise means for applying a double reenforcement to the sewing thread, which means may be associated with the sewing machine disclosed in the aforementioned patent to Robert N. Cundall without modification thereof, and which may be operated by the operating mechanism disclosed in said patent without modification thereof.

Another object of the present invention is to devise means for allowing the retraction of the sewing. machine presser foot without necessitating dismantling of the reenforcing thread mech- I anism whether said mechanism is to apply two threads or only one as in said prior patent to Robert N. Cundall. I

Another object of the present invention is to devise means to create a condition upon the needle side of the seam simulating as much as possible the condition of the looper side of a seam created by a double-thread, interlocked chain stitch machine. It has been determined by lengthy observation that the looper side of the seam, due to the reenforcing action of the interlocked looper thread, will withstand most shocks to which such a seam may be subjected. In accordance with the disclosure of the aforementioned patent of Webster Noyes Baker, it has been found that the application of a reenforcing cord of the type and size therein disclosed, to the needle side of the seam only, will create effective closures for bags and seams for multi-ply articles. The present invention contemplates the use of two reenforcing threads of substantially the same type and size as the sewing threads, so placed with respect to the stitches of the needle thread as to cause the needle side of the seam to approximate the looper side of the seam in strength and resistance to tearing.

Referring to the accompanying drawings wherein like numerals refer to like parts throughout, there is disclosed the preferred form of the invention wherein Fig. 1 is an elevational view of a sewing machine, having the reenforcing thread applying drive disclosed in the aforementioned patent of Robert N. Cundall, and the reenforcing thread applying means of the present invention, associated therewith, the latter means being disclosed in a section taken along the line of l-l of Fig. 2; Fig. 2 is a horizontal section taken along line 22 of Fig. 1;

Fig. 3 is an elevational view of a portion of the mechanism taken along line 3,-3 of Fig. 4;

Fig. 4 'is a vertical cross-section taken along line 44 of Fig. 1;

Fig. 5 is a vertical section taken along line 5-5 of Fig. 2, showing the beginning of a cycle of operation;

Fig. 6 is a similar view showing an intermediate phase of a cycle of operation;

Fig. '7 is a similar view showing substantially the median position of a cycle of operation;

Fig. 8 is a partial view of a bag having reenforcing threads applied thereto, the view being taken on the needle thread side of the seam; and

Fig. 9 is a similar View of the opposite side of the bag, showing the naturally reenforced structure of the looper side of the seam.

Referring to Fig. 1, there is disclosed the frame 20 of a sewing machine, partially broken away and partially diagrammatic. The sewing machine is provided with a throat portion 2| through which the material may pass and with a presser foot 22 and throat plate 23 between which the material is guided during the stitching action. The material, such as a bag mouth A, is fed forward by means of a feed dog 24, operated by mechanism preferably as .disclosed and claimed in the copending application of Robert N. Cundall and Lincoln A. Cundall, Serial No. 690,988, filed September 26, 1933. Between forward movements of the material it is pierced by a needle 25, carrying a needle thread 26, with which cooperates a looper 21 carrying a looper thread 28, preferably as disclosed and claimed in the copending application of Howland F. Briggs and Robert N. Cundall, Serial No. 757,080, filed December 12, 1934, thereby creating a double thread interlocked chain stitch seam of which the looper side is formed substantially as illustrated in Fig. 9.

As. disclosed in the aforementioned patent to Robert N. Cundall, a shaft 30, mounted upon the frame 20 is rotated by a gear 3| meshing with a gear associated with the sewing machine driving shaft, the gear ratios being such that shaft is imparted half the speed of rotation of the driving shaft, whereby two cycles of the sewing machine will occur for every one complete revolution of. shaft 38. Shaft 30 is provided with an eccentric 32 to which is attached a link 33 extending to a crank 34fixed to a rock shaft 35 mounted in the lower portion of the frame. The leverage ratio of eccentric 32 and lever 34 are such that rock shaft 35 is rocked rather than completely rotated. The foregoing reenforcing thread applying means drive is substantially as disclosed and claimed in the aforesaid patent of Robert N. Cundall, No. 1,963,652.

In the present invention the forward end of rock shaft 35 is provided with a double-armed lever of which the upper arm is in vertical alignment with the lower arm. The upper arm connected to a link 4| extending to a crank 42 pivotally mounted upon the presser foot supporting rod 43. The lower arm is provided with a link 45 extended upward over the needle and pivoted to a crank 46, likewise pivotally mounted upon the presser foot rod 43. The length of crank 42 is the same as the upper arm, and the length of crank 45 is the same as the length of the lower arm of lever 43, whereby cranks 42 and are coextensively rocked in opposite directions, in accordance with the rocking. of rock shaft 35. The lower side of the hub of crank 42 supports a lower reenforcing thread guiding arm 50, and projection 5| of the hub of crank 46 supports an upper reenforcing thread guiding arm 52. The arms are angularly extended forward of links ii and 45 and about the needle 25 and needle bar the upper arm being forward. of the lower arm in order that they may cross, as illustrated in Fig. '7. The extremities of the guiding arms are provided with eyes through which the reenforcing threads are passed, reenforcing thread 55 being guided by an eye 55 mounted upon the upper extremity of presser foot 22 and the eye. in upper guide arm 52, the other reenforcing thread 57 being guided by an eye 58 mounted upon the lower side of presser foot 22 and by the eye in lower guiding arm 50. The reenforcing threads extend to the surface of the work and become bound beneath the loops of the needle thread. In Fig. 5 the arms are separated as the needle enters the work, thereby allowing the needle and needle thread to pass between the reenforcing threads. In Fig. 6 the needle is about to be retracted from the Work, and in Fig. '7, as the needle is entering the work for a second stitch, the arms have completely crossed the reenforcing threads to the opposite sides of the needle, resulting in the formation of a reenforced seam such as disclosed in Fig. 8. Comparison of Figs. 8 and 9 will disclose that the seam is substantially as well reenforced on one side of the bag or material being sewn as on the other.

It is occasionally necessary to withdraw the presser foot from proximitywith the throat plate, and for this reason as well as to accommodate various thicknesses of material, the presser foot rod 43 is surrounded by a spring 60 against which the presser foot may be retracted. In order that the upper guide arm 52 may not interfere with retraction of the presser foot it is pivotally mounted upon the extension 5| and is provided with a rearwardly and downwardly extending abutment 6|. A spring 62 extends from the abutment to the frame of the machine, whereby the guiding arm is normally held in the position of Fig. 2 by the abutment 5| bearing against the hub of crank 46. Upon retraction of presser foot 722, spring 62 allows the arm to be retracted against thev tension of the spring, whereby the necessity of dismantling the device is obviated.

Modifications in detail and arrangement of the present invention may be apparent to those skilled in the art and are intended to be included within the scope of the following claims:

We claim:

1. A double-thread, interlocked chain stitch sewing machine, comprising a machine frame, a presser foot rod resiliently mounted in said frame for guiding material through the machine, a needle reciprocally mounted in said machine frame adapted to pierce the material being sewn at stitching intervals, alooper mounted in said machine frame, a needle thread supplied to said needle and. a looper thread supplied to said looper, mechanism for cooperatively actuating said needle and said looper to form a seam with said threads, and meansassociated with said needle operated bysaid actuating mechanism in synchronism with the needle and looper to shift each of two reenforcing threads alternately to opposite sides of the needle at each reciprocation thereof,v said reenforcing threads being thereby bound beneath the stitches of the needle thread to reenforce the seam, said means comprising a pair of reenforcing thread guiding arms having eyes at their ends coextensively rocked to move said eyes to opposite sides of the needle, and a rock shaft and linkage connected there with, said rock shaft performing a complete cycle of operation for every two reciprocations of said needle, said guiding arms being pivotally mounted upon said presser foot rod and being angularly extended past opposite sides of said needle and extended forwardly in spaced relation to each other, the most forwardly extending of said arms being resiliently retained in position and capable of pivotal retraction toward the other of said arms.

2. Means for applying a reenforcing thread beneath the stitches of the needle thread in a seam formedby a needle and cooperating mechanism comprising, an arm pivotally mounted adjacent said needle and angularly bent about said needle, said arm having a guiding eye in its extremity through which said reenforcing thread passes to the seam, means to rock said arm about its mounting to shift its extremity alternately to opposite sides of the needle, the rocking of said arm being timed to cause said reenforcing thread to pass from one side of the needle to the other at each stroke thereof, a second pivotal mounting for said arm about which said arm may be swung away from the plane of its operating movement, and means resiliently retaining said arm in 5 normal operating position.

LINCOLN A. CUNDALL. ORME E. CHEATHAM. 

